1. Field of the Invention
The present invention relates to a single-phase photovoltaic inverter and a control method thereof, and more particularly, to a single-phase photovoltaic inverter and a control method thereof in which a small insulated transformer and an ordinary current transformer are used to measure a leakage current instead of a high-priced specific current transformer that is only used to measure a leakage current.
2. Background of the Invention
In general, a single-phase photovoltaic inverter (or a grid tied inverter) is a device that converts direct current (abbreviated as “DC” hereinafter) energy supplied from a photovoltaic module into alternating current (abbreviated as “AC” hereinafter) energy and provides the converted AC current to a single-phase alternating current grid (or electric load).
Such a photovoltaic module has a positive (+) polarity and a negative (−) polarity which are connected to a photovoltaic inverter. When the positive and negative polarity cables of the photovoltaic have damages, wiring errors, or defects, dielectric breakdown and leakage currents occur.
Excessive leakage current may cause a single-phase photovoltaic inverter to be burned out and also harm a worker's body when the worker grasps the positive and negative polarity cables.
In addition, since a current transformer that is only used to measure such a leakage current is produced for a special purpose rather than a general purpose, the current transformer is very expensive and thus increases the total production cost of a power generation system.
Furthermore, a method of measuring such a leakage current has a non-insulated type. Thus, when an abnormal fault such as a ground fault or electric shortage occurs at a photovoltaic module side, a fault current or a fault voltage may be applied to a leakage current measuring unit at an input side of a single-phase photovoltaic inverter, thus burning out the high-priced current transformer that performs a precise measurement.